What the Social Brain Sciences Can Tell Us About the Self Todd F. Heatherton, C. Neil Macrae, and William M. Kelley Department of Psychological and Brain Sciences, Dartmouth College ABSTRACT—Social brain science is an emerging interdisciplinary field that encompasses researchers who use the approaches of evolutionary psychology, social cognition, and especially neu- roscience to study human social nature. The advent of brain imaging and other cognitive neuroscience methods has provided researchers with new tools to explore the social mind. We de- scribe how these methods can be used to explore the perplexing question of self, for example, resolving long-standing debates regarding theories of self-referential memory and providing novel insights into other aspects of self. KEYWORDS—self; self-referential memory; self-recognition; fMRI; prefrontal cortex Social brain science is an emerging field that encompasses re- searchers who combine approaches of evolutionary psychology or social cognition with neuroscience to study the neural underpinnings of social behavior (Adolphs, 2003). From an evolutionary perspective, the brain is an organ that has evolved over millions of years to solve problems related to survival and reproduction. Those ancestors who were able to solve survival problems and adapt to their environments were most likely to reproduce and pass along their genes. For humans, some of the most pernicious adaptive challenges involve dealing with other humans. These challenges include selecting mates, cooperating in hunting and gathering, forming alliances, competing over scarce resources, and even warring with neighboring groups. Unlike many animal species, humans are not born precocious; they require sub- stantial effort and resources from caregivers, who themselves are re- liant on other group members for survival. Therefore, behaviors such as lying, cheating, or stealing are discouraged by social norms in all societies because they decrease survival and reproduction for other group members. It has even been proposed that humans have ‘‘cheater detectors’’ that are highly efficient at spotting individuals who violate social contracts (Cosmides & Tooby, 2000). This dependency on group living is not unique to humans, but the nature of relations among and between in-group and out-group members is especially complex in human societies. THE SOCIAL BRAIN Just as certain regions of the brain seem specialized for walking, talking, and breathing, the brain has developed specialized mecha- nisms for dealing with the social environment. Indeed, since the 19th century, it has been known that damage to certain brain regions (e.g., medial prefrontal cortex, or MPFC, the brain region behind the middle of your forehead) interferes with social competence while not affecting competence in other domains. More recently, there has been a growing interest among social psy- chologists and cognitive neuroscientists in using brain imaging to study social cognition. Using these methods, researchers have identified a number of brain regions that appear to support highly specialized social capacities, such as theory of mind (e.g., understanding other people’s mental states), social emotions (e.g., empathy), recognition of faces and their emotional expressions, judgments of trustworthiness and attrac- tiveness, and cooperation. Collectively, such studies suggest that people are often given privileged status by the brain as it processes objects in the environment. For example, recent work has shown that different brain regions are engaged when people make meaning-based judg- ments about people, as opposed to similar judgments made about other objects (Mitchell, Heatherton, & Macrae, 2002). Social brain science is providing new insights into long-standing questions regard- ing social behavior. In the remainder of this article, we discuss the use of neuroscience methods to study various aspects of the self. THE SELF A unitary sense of self that exists across time and place is a central feature of human experience, at least for most people. Understanding the nature of self—what it is and what it does—has challenged scholars for many centuries. Although most people intuitively understand what is meant by the term self, definitions have tended toward the philosoph- ical and metaphysical. Efforts at creating more formal definitions have largely been unsuccessful, as many features of self are empirically murky, difficult to identify and assess using objective methods. Yet the phenomenological experience of self is highly familiar to everyone. So, at issue is not whether the self exists, but how best to study it. Scientific progress in understanding the nature of self was stifled by the inherent subjectivity and ambiguity that plagued much of the early research on the topic. Although social and developmental psycholo- gists have made considerable advances in identifying behaviors that are related to the self, our focus here is on how the rise of cognitive Address correspondence to Todd F. Heatherton, Department of Psychological and Brain Sciences, 6207 Moore Hall, Dartmouth College, Hanover, NH 03755; e-mail: todd.f.heatherton@dartmouth. edu. CURRENT DIRECTIONS IN PSYCHOLOGICAL SCIENCE 190 Volume 13—Number 5 Copyright r 2004 American Psychological Society